Seattle City Council President Richard Conlin on Thursday turned away Mayor Mike McGinn’s proposal to establish a long-term homeless encampment at the former Sunny Jim site in Sodo.

In a letter to McGinn, Conlin and three other council members said state law requires an environmental review before zoning changes can be considered and a residential facility located in an industrial area.

“We share your concern for those who are homeless and your willingness to consider innovative ways to get people into safe, decent shelter,” Conlin wrote. “… The Council will consider the proposed legislation when we can legally do so.”

McGinn said he was struck by the contrast between the council’s handling of the deep-bore tunnel project and the homeless encampment.

“They approved agreements with the state (for the tunnel) even though the environmental review is far from complete,” McGinn said. “I think they’re wrong as proven by their own practices.”

McGinn proposed locating the homeless encampment at the site of the former Sunny Jim peanut-butter factory, which burned down in September. The mayor’s plan was to create an alternative to tent cities such as Nickelsville that have to move every 90 days.

McGinn proposed housing up to 150 residents and building temporary facilities for offices, eating and showering.

When he announced the plan, McGinn suggested the encampment could be up and running by March, but he then extended that timeline to October after concerns about contamination at the site.

Last month, McGinn released a study by a consultant that said the contamination could be easily addressed.

The Sodo Business Association has raised concerns about the appropriateness of the site on Airport Way South.

Mike Peringer, president of the association, said Thursday his group opposed the location because it isn’t convenient to social-service organizations or public transit.

To use the Sunny Jim site for a homeless encampment, the City Council would have to approve zoning to allow a residential facility in an industrial zone.

The mayor had said the city’s Finance and Administrative Services Department could make the improvements, though the City Council had not approved any funding.

At a Wednesday news conference, McGinn said he was aware of council concerns about the encampment, but he questioned whether council members were trying to find solutions or “kill the encampment proposal.”

Councilmember Sally Bagshaw, who signed the letter along with Nick Licata and Sally Clark, said Thursday the council shares the mayor’s desire to address the issue of homelessness. But, she said, estimates to clean the site, install facilities and hire supervisors came to about $1 million over the next two years.

For that same amount, Bagshaw said, the city could buy a building, provide single-occupancy rooms and get people out of temporary shelters.

Bagshaw said the council and mayor agree on the goals and can work together to come up with another proposal.